MONTERREY, Mexico — Soldiers killed at least 25 suspected cartel members Thursday in a raid and gunbattle in a Mexican state near the U.S. border that has become one of the most dangerous battlegrounds in the country’s drug war.

A military aircraft flying over Ciudad Mier in Tamaulipas state spotted several gunmen in front of a building, according to a statement from Mexico’s Defense Department.

When ground troops moved in, gunmen opened fire, starting a gunbattle in which 25 suspected cartel members died, according to the military. The statement said two soldiers were wounded.

Authorities rescued three people believed to be kidnap victims in the raid, according to the statement. The military said troops seized 25 rifles, four grenades, 4,200 rounds of ammunition and 23 vehicles.

Earlier, a military spokesman said the gunmen were believed to be on a property controlled by the Zetas, who started out as a gang of drug assassins but have since evolved into a powerful cartel.

Violence has surged in northeastern Mexico this year since the Zetas broke ranks with their former employer, the Gulf cartel, resulting in a flare-up of drug violence in Tamaulipas.Last week, marines discovered the bodies of 72 Central and South American migrants believed to have been gunned down by the Zetas after refusing to work for the cartel, in what may be the deadliest drug gang massacres to date. The migrants’ bodies were discovered at a ranch about 100 miles (160 kilometers) from the U.S. border in Tamaulipas.

Five days later, the mayor of the Tamaulipas town of Hidalgo (Marco Antonio Leal Garcia), bordering Nuevo Leon state, was ambushed and killed in his car in an attack that also wounded his four-year-old daughter.

In June, gunmen ambushed and killed the leading candidate for state governor a week before regional elections. And in May a mayoral candidate in Tamaulipas was assassinated.

Drug violence has claimed more than 28,000 lives since President Felipe Calderon intensified a crackdown on cartels after taking office in late 2006.

Over the weekend, 17 people were injured in four separate bomb attacks in Tamaulipas in just 24 hours.

The explosions appeared to target places connected with an investigation into the killing of 72 foreign migrants whose bodies were found on a ranch in the state on 25 August.

The 58 men and 14 women were from South and Central America. They had been trying to reach the US, and were believed to have been killed by members of the Zetas gang.

Shortly after the grim discovery of their bodies, Roberto Suarez, the detective leading the investigation into the mass slaying, went missing, along with a police officer he was travelling with.

The rising violence has led to growing criticism of President Felipe Calderon’s military crackdown on Mexico’s drug gangs. Opposition groups say the crackdown, which began three and a half years ago, has done nothing to stop the flow of drugs to the US.

In his state of the union address on Thursday morning, the president admitted the violence was worsening but defended his approach, saying the cartels were being weakened.

“The capture or killing of important criminal leaders has made the crime organisations more desperate,” Mr Calderon said.

“It is an ever more bloody war between organised crime groups fighting for territory, markets and routes.”

Mr Calderon insisted the fight had to go on.

Rodolfo Torre Canto: Gubernatorial candidate assassianted by cartels

“If we want a safe Mexico for the Mexicans of the future, we must take on the cost of achieving it today,” he said.

More than 28,000 people have died in drug-related violence in Mexico since Mr Calderon ordered the army and federal police to fight the cartels in 2006.

Pedro Brito Ocampo – National Action Party (PAN) manager in the Guerrero state municipality of Heliodoro Castillo. His body, found in an abandoned house, had 40 gunshot wounds.

June 19, 2010

Jesús Manuel Lara – 48 year-old Institutional Revolutionary Party (PRI) mayor of Guadalupe Distrito Bravo, Chihuahua, died in a house in the Santa Teresa neighborhood of Ciudad Juárez when a group of gunmen burst in and shot him.

May 21, 2010

Jorge Rogelio Ortega Ortega – Institutional Revolutionary Party (PRI) associate helping with the political campaigns, gunned down by heavily armed men riding in a Ranger pickup.

May 13, 2010

Mario Guajardo Varela – National Action Party (PAN) candidate for mayor of Valle Hermoso, Tamaulipas, his son, Luis Mario Guajardo Adame, and an employee named Fernando Treviño, were executed by three hitmen inside an agricultural supply store.

March 17, 2010

Sótico Silvestre López – Democratic Revolutionary Party (PRD) manager in San Andrés Huaxpaltepec, a municipality on the coast of Oaxaca, was gunned down by a group of assassins.

A memorial of flowers and candles took up yards of sidewalk Friday near the bullet-riddled cafeteria where a former mayor who had promised to rid this city of drug corruption was gunned down the previous day. Juan Antonio Guajardo Anzaldua, a father of four, would have turned 49 on Friday. He was shot dead at 5:38 p.m. Thursday at his family-owned restaurant, along with two bodyguards and three other people.